Cigarette filters



eral formula:

3,340,879 CIGARETTE FILTERS Henry George Horsewell, Totton, and Graham Harry Rayner, Portsmouth, England, assignors to Brown & Williamson Tobacco Corporation, Louisville, Ky., a corporation of Delaware No Drawing. Filed Jan. 16, 1967, Ser. No. 609,343

Claims. (Cl. 131-267) ABSTRACT OF THE DISCLOSURE Tobacco smoke filter formed of filamentary or sheet tobacco smoker filter material treated with a solution of poly(alkyleneimine) for reducing the content of the more volatile acidic constituents of tobacco smoke while maintaining substantially the flavorful qualities of the tobacco smoke.

This application is a continuation-in-part of our application Ser. No. 385,490, filed July 27, 1964, now abandoned.

Background of the invention tion'or. adsorption on a suitable surface or by'chemical reaction.

Of these less pleasant constituents, the presence of the more volatile phenolic and acidic compounds may be undesirable; f

It is known that the volatile acidic. compounds of tobacco smoke may be reduced by the addition of alkaline salts to filter material or to the tobacco itself. Also, by mechanically altering the filter material in which the draw resistance is increased, a greater quantity or proportion of the particulate material, such as tar and nicotine, may be removed.

Summary of the invention According to the invention, filamentary or sheet tobacco smoke filter material is treated with a poly(alkyleneimine). The poly(alkyleneimine) may be applied to the bulk filter material in a solution or suspension of a mixture of water and an organic solvent. Any of the conventional means known to the art may be employed for applying the poly(alkyleneimine) to the filter material, for example, as by spraying, soaking, dipping, painting or the like.

The poly(alkyleneimines) utilized in the present invention are substantially nonvolatile and have the genwhere each R is individually selected from the class consisting of hydrogen, lower alkyl radicals free from aliphatic unsaturation and having from 1 to 6 carbon atoms H and n is a whole number greater than 12.

. weight ofthe filter material; preferably about 0.5%; an

more preferably from about 0.5% to 3.0%.

Detailed description of the invention In accordance with the present invention, We have unexpectedly discovered that theuserof ,a substantially nonvolatile high molecular weight poly(alkyleneimine) avoids the difficulties presented by the treating materials of the prior art and that such a treated smoke filter provides a novel means for reducing the content of the more 5 volatile constituents of tobacco smoke while maintaining substantially the flavorful qualities of the tobacco smoke.

- The poly(alkyleneimines) utilized in the present invention have the general formula:

where each R is individually selected from the class consisting of hydrogen, lower alkyl radicals free from aliphatic unsaturation and having from 1 to 6 carbon atoms 5 and n is from about 23 to 1150. The polymers of formula (1) are formed from cyclic monomers having the formula:

where R is as previously defined. The polymers of Formula l,'formed from the monomers of Formula 2, differ from other materials which have also been designated 5 poly(alkyleneimines) in that, regardless of the nature of the substituent R, two carbon atoms and one nitrogen atom alternate along the polymeric chain. The substituents R remain substituents on the polymer chain after polymerization, and are not incorporated into the back- 3 bone. Thus, the irnine value of the poly(alkyleneimines) of Formula 1 are significantly higher than other polymers which have been referred to as. poly(alkyleneimines), suchas those with the repeating structure:

where a is a whole number greater than 1. 'As previously mentioned, the substituents R in Formulas 1 and 2 can be hydrogen or phenyl. Additionally, R can represent a lower alkyl radical, such as, methyl, methyl, propyl, isopropyl, butyl, amyl andhexyl. Standard names have been assigned to the various monomeric ethyleneimines. For example, when each R in Formula 1 2 is hydrogen, the monomer is called either ethyleneirnine or aziridine. If one R is methyl, and the other R's are hydrogen, then the monomer is propyleneimine' or 2- methyl aziridine. The various monomers of Formula 2 are easily polymerized by known methods. Among the polymers which can be formed from the monomers of Formula 2, which are useful in the present invention, are poly(ethyleneimine), poly(propyleneimine), poly( 2-ethyl aziridine), poly(2,2-dimethyl aziridine), and poly(2,2-dimethyl-3-n-propyl aziridine).

The poly(alkyleneimines) employed as the treating material for tobacco smoke filter material are substantially nonvolatile and are not transferred to the smoke stream when tobacco smoke passes therethrough. Where the poly(alkyleneimine) is poly(ethyleneimine) it is substantia'lly nonvolatile when n of Formula 1 is at least 13 which corresponds to a molecular weight of about 600. Negligible, if any, transfer of poly(alkyleneimine) occurs where n' is approximately 23 which corresponds to a molecular weight of about 1000 for poly(ethyleneimine).

Since the viscosity of the poly(alkyleneimines) increases as their molecular weight increases, their ease of application to tobacco smoke filter material becomes more diflicult. We have found that by mixing an organic solvent with an aqueous mixture of poly(alkyleneimine) relative ease of application is maintained even when n is as high as 1150 which corresponds to a molecular weight of about 50,000 for poly(ethyleneimine).

For example, a treatment solution of 50% by weight poly(ethyleneimine) and water is mixed with ethyl alcohol to reduce the viscosity of the aqueous solution and to increase its ease of application to tobacco smoke filter material. Any relatively volatile organic solvent may be employed to reduce the viscosity of an aqueous poly (alkyleneimine) solution. Such solvents may be, for example, methyl, ethyl, propyl, isopropyl alcohols or other organic solvents for poly(alkyleneimines) which are volatile and are not reactive thereto under conditions of treatment.

Therefore, a range for n of Formula 1 may be at least 13 and preferably 23 to 1150.

Smoke filter treating materials have been disclosed in the prior art which contain amine or imine groups. However, not only have the materials been different, but their action on the smoke being filtered has been quite different from the action of the poly(alkyleneimines) of the present invention. Materials disclosed in the past have included ionic resins and salts, low molecular weight diamines, amides, and compositions of matter containing materials other than imines. In the case of the low molecular weight materials, there is a significant problem in transfer of the material through the filter along with the smoke. The other materials, being either acidic or very slightly alkaline tend not only to reduce the acidic components of tobacco smoke but, additionally, the flavorants, such as nicotine, are also reduced or removed from the tobacco smoke. Further, the addition of some of these treating materials increases the pressure drop through the filter, or the material itself transfers to the tobacco smoke, thereby making it much more diflicult to draw the smoke through the filter and further reducing the desirability of the filtered cigarette.

Poly(alkyleneimines) are alkaline materials and, as such, have a selective effect on the smoke being treated. The tobacco smoke filters treated with high molecular weight poly(alkyleneimines) of Formula 1 reduce the more volatile acidic components of tobacco smoke, such as phenolics and other acidic components, while allowing a major proportion of the more desirable flavorants, such as nicotine, to pass. Because of the structure in which one imine group alternates with two carbon atoms along the chain, a multitude of reactive imine sites is available to remove acidic components from smoke. This is in particular contradistinction to other polymers which have been referred to as poly(alkyleneimines) which have a much lower imine value. Further, because of the high molecular weight of the poly(alkyleneimines) utilized in accordance with the present invention, and consequent low volatility of the materials, the transfer of the treating materials through the filter is, at most, negligible. An additional advantage to this negligible transfer is that essentially the full amount of treating material originally applied to the filter remains in the filter throughout the commercial life of the item to which it is applied, such as a cigarette.

As just mentioned, the reactivity of the poly(alkyleneimines) for the acidic components in the smoke is at the site of the imine linkage in the polymer, more particular ly the reactive hydrogen bonded to the nitrogen. Since the polymers reactivity is at this imine linkage, and since a molecular weight of about 600, preferably about 1,000, is suflicient to prevent transfer of the treating agent to the smoke through excess volatility, there is no particular advantage to substituting the carbon atoms in the polymer chain. Therefore, the preferred polymer are those formed from ethyleneimine and from Z-methyl aziridine, that is:

and

where n is as previously defined.

The method of carrying out this invention will be more fully described in the following examples:

EXAMPLE I A 50% aqueous solution of poly(ethyleneimine), available commercially under the trade name Polymin P," was diluted with water to give a solution containing 3.75% active constituent. Two mls. of this solution was sprayed onto a strip of crimped absorbent paper, as used in the manufacture of cigarette filters, weighing 0.7-0.8 gms. The concentration of the solution was such that, after the treated paper had been dried overnight at room temperature (20-25 C.), the paper contained 10% by weight of the polymer. The treated paper was then hand rolled into rods mm. long and of cigarette diameter, from which 15 mm. blank were cut and attached as filter plugs to cigarettes. Untreated filter rods were similarly prepared except that they were sprayed with water only. The cigarettes were then smoked by an automatic machine at one putt/min, each puff being of two seconds duration and a volume of 35 mls. The smoke obtained was analyzed and compared with that obtained from cigarettes with untreated filters.

EXAMPLE II Other filters were prepared as in Example I, except that the paper contained a final concentration of 50% by weight of the polymer, and the smoke produced in similar tests was analyzed.

EXAMPLE III Other filters were prepared as in Example I, except that the paper contained a final concentration of 1% by Weight of the polymer, and the smoke produced in similar tests was analyzed.

EXAMPLE IV Other filters were prepared as in Example 1, except that the paper contained a final concentration of 3% by weight of the polymer, and the smoke produced in similar tests was analyzed.

The results obtained from the comparative tests of Examples I through IV are given in Table 1 A 50% aqueous solution of poly(ethyleneimine), available commercially under the trade name Polymin P, was diluted with water to give a solution containing 2% active constituent. Two mls. of this solution was sprayed onto cellulose acetate tow, with a total denier of 57,000 and a denier per filament of 2.1, and formed into a filter rod 90 mm. in length and of cigarette diameter and was immediately freeze dried to remove the water. The concentration of the solution was such that the treated filter, after readjustment to room temperature and humidity, contained 8% by weight of the polymer. Cigarette filters 15 mm. in length were cut from the treated rods and attached as filter plugs to cigarettes, and the cigarettes smoked as in Example I.

EXAMPLE VI Other filters were prepared as in Example V, except that the treated filters contained a final concentration of 26% by weight of the polymer. Smoke from cigarettes provided with the treated filters was again analyzed.

EXAMPLE VII Other filters were prepared as in Example V, except that the treated filters contained a final concentration of 1% by weight of the polymer. Smoke from cigarettes provided with the treated filters was again analyzed.

EXAMPLE VIII Other filters were prepared as in Example V, except that the treated filters contained a final concentration of 3% by weight of the polymer. Smoke from cigarettes provided with the treated filters was again analyzed.

The results obtained with Examples V through VIII are given in comparison with those from untreated filter cigarettes in Table 2:

A continuous strip of 11 /2" wide open-mesh creped wadding (such as Schweitzer paper) was passed under a sponge roller and roller coated with a 50% aqueous solution of p0ly(ethyleneimine), available commercially under the trade name Polymin P, was diluted with water to givefa solution containing 2% active constituent. The rate of travel of the paper was arranged so that the final concentration of poly(ethyleneimine) on the paper was 6% by weight. The paper was then hot air dried and formed into a continuous filter rod using conventional rod-forming machinery. The treated rod was cut into 15 mm. lengths which were attached to cigarettes and smoked in the manner described in Example I.

EXAMPLE X Other filters were prepared as in Example IX, except that the treated filters contained a final concentration of 1% by weight of the polymer. Smoke from cigarettes provided with they treated filters was again analyzed.

EXAMPLE XI Other filters were prepared as in Example IX, except that the treated filters contained a final concentration of 3% by weight of the polymer. Smoke from cigarettes provided with the treated filters was againanalyzed.

The results obtained with Examples IX through XI are given in comparison with those from untreated filter cigarettes in Table 3:

Similar results to those obtained above are obtained when creped wadding is treated with similar solutions of polymers of propyleneimine or 2-ethyl aziridine having similar chain lengths.

6 EXAMPLE x11 To show the increase in efiiciency for reducing the content of the more volatile acidic constituents of tobacco smoke, two filters were prepared, using the same materials and procedures as in Example V, but providing a 10% concentration of poly(ethyleneimine) of approximate average formula:

This polymer corresponds to generic Formula 1 where n is 15 and each R is hydrogen. A second filter was prepared, corresponding in every respect to that just described, except that the poly(ethyleneirnine) was of approximate average formula:

(6) NH (OH CH NH) H The poly(ethyleneimine) of Formula 6 corresponds to generic Formula 1 where each R is hydrogen and n is 19. The treated filters (15 mm. in length) were attached to cigarettes and the cigarettes smoked as in Example 1. The results obtained are shown in Table 4:

TABLE 4 1', Percent removal of smoke constituents Tar Nicotine HON Phenol A second comparison of increa sed efliciency utilizing longer chain length poly(alkyleneirnines) was performed,

in this example, using a viscose filter material. The

method of treatment-employed was the same as that in Example I and the comparative smoking test was similarly performed. The results of the comparison, using viscose as the filter material, are shown in Table 5:

TABLE 5 n Percent removal of smoke constituents Tar Nicotine HON. Phenol i333: Z2 3% 32 E2 U From the results shown in Table 5 it can be seen that by increasing the chain length of the poly(alkyleneimine) used with viscose, while the nicotine filtration efficiency is essentially unchanged, more of the tar is removed, and significantly greater amounts of the hydrogen cyanide and phenol are removed from the smoke.

Similar results to those shown above are obtained using similar solutions of polymers of 2,2-dimethyl aziridine with the same chain lengths.

EXAMPLE XIV To better show the tendency of a filter treated with a poly(alkyleneimine) to allow the passage of nicotine,

while reducing the acidic constituents in the smoke, various filters were made and the amount and type of materials passing through the filter measured. The filters were formed in the same manner and with the same materials as in Example VI and tested in the manner described in Example I. The filter had a particulate retention of 50%. In Table 6, the results of these tests are shown:

TABLE 6 Percentage passed through with smoke Tar/Nicotine Filter ratio Tar Nicotine e) 2-) None 2O 2 i 1 l0 imine) 10 1. 28 7. 8 Treated with 12% poly(ethyleneimine) 10 1. 42 7 From these results it can be seen that an untreated filter will indiscriminately remove acidic constituents and fiavorants. The addition of about 6% poly(ethyleneimine) did not impair the efficiency of the filter in removing tar, but :allowed additional nicotine to pass, thus lowering the tar to nicotine ratio. A further improvement in this ratio, and in the amount of nicotine allowed to pass, is shown by the filter treated with 12% poly(ethyleneimine).

As stated above, a volatile organic solvent may be employed for mixing with an aqueous solution of poly (alkyleneimine) to make the application more uniform and facile to the filter material while maintaining the desired amount of active constituent applied to the material. Thus, an organic solvent, such as ethyl alcohol, may be employed as a portion of the aqueous mixture in the specific examples herein with no change in the filtration efiiciency of the treated filter material.

Most advantageously the poly(alkyleneimine) is applied to the cigarette filter material as a solution containing from about 0.5% to 50.0% of the poly(ethyleneimine) in water. Any of the fibrous masses employed in the art as cigarette filter materials can be used with the present invention. For example, a mass of parallel fibers, such as a tow of cellulose acetate filaments, can be utilized. Additionally, the filter body can comprise a wad of paper, or bats interleaved with paper and rolled into a convoluted configuration. Additionally, thermoplastic filter fibers other than cellulose acetate can be employed, such as viscose, cotton, and polyesters. Further, additives, known to art, which do not interfere with the functioning of the poly(alkyleneimine), or react with it, can also be employed to treat the filters utilized in accordance with the present invention. The amount of poly(alkyleneimine) deposited on the filter should vary from 0.5% to 50.0%, preferably 0.5% to 3.0%, by weight of the filter material.

While specific embodiments of this invention have been described, it is apparent that many variations can be employed without departing from the spirit and scope of the present invention.

We claim:

1. A tobacco smoke filter comprising fibrous tobacco smoke filter material treated with a poly(alkyleneimine) of the average formula:

where each R is independently selected from the class consisting of hydrogen, lower alkyl radicals free of aliphatic unsaturation having from 1 to 6 carbon atoms and n is at least 13.

2. A tobacco smoke filter comprising fibrous tobacco smoke filter material treated with a poly(alkyleneimine) of the average formula:

where each R is selected from the class consisting of hydrogen, lower alkyl radicals free of aliphatic unsaturation having from 1 to 6 carbon atoms and n is at least 13, in an amount of at least 0.5 by weight, based on the weight of the tobacco smoke filter material.

3. The tobacco smoke filter of claim 2 wherein n is from 23 to 1150.

4. A tobacco smoke filter of claim 2 wherein the poly(alkyleneimine) is a material selected from the group consisting of poly(ethyleneimine), poly(propyleneimine), poly(2-ethyl aziridine), poly(2,2-dimethyl aziridine), and poly(2,2-dimethyl-3-n-propyl aziridine).

5. The tobacco smoke filter of claim 4 wherein the poly(alkyleneimine) is poly(ethyleneimine).

6. The tobacco smoke filter of claim 4 wherein the poly(ethyleneimine) is in an amount of 0.5% to 3.0%.

7. The tobacco smoke filter of claim 4 wherein the poly(alkyleneimine) is poly(2-methyl aziridine).

'8. A tobacco smoke filter comprising fibrous tobacco smoke filter material treated with a poly(alkyleneimine) having a relatively high molecular weight of at least 600.

9. The tobacco smoke filter of claim 8 wherein the poly(alkyleneimine) is poly(ethyleneimine).

10. The tobacco smoke filter of claim 9 wherein the poly(ethyleneimine) is in the amount of from 0.5% to 50.0% by weight, based on the weight of tobacco smoke filter material.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 1/ 1962 Canada.

SAMUEL KOREN, Primary Examiner.

D. J. DONOHUE, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,340,879 September 12, 1967 Henry George Horsewell et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 13, for "smoker" read smoke 11ne 66, after "0.5%" lllSGT'C to 50% Signed and sealed thls 6th day or August 1968.

(SEAL) Altcst:

Edward M. Fletcher, J1. EDWARD BRENNER Altesting Officer Commissioner of Patents 

1. A TOBACCO SMOKE FILTER COMPRISING FIBROUS TOBACCO SMOKE FILTER MATERIAL TREATED WITH A POLY(ALKYLENEIMINE) OF THE AVERAGE FORMULA: 